Ran a drop ship business years ago with medical equipment. Made a deal with a couple of suppliers. Don't know if it still is but it used to be the way to go if you didn't want the overhead of inventory. Not as much compitition back then either, as internet was a non profit toy.
Actually was considering to do it again but I think King 11 parts are much to limited.
Figured you took off the blue coating, as only seen them painted.
Went to Kyles site, He seems to have a large selection of motors. I keep seeing 4000K motors popping up for kings but thats way too fast for most applications as you have drop way down on Pinion size to like 8-9 tooth and I think thats too much of a load on the main gear with only 1 tooth in full engagement. Trex had a step down arrangement which allows them to use a 12-15 tooth pinion.
I see though that he has the HDX/Sonix type motors have to look over his site a little more.
Nice to find a alternative to the 3800 that is about the same price. Notice that the 3800-3900 seem to last forever while all the others burn up or have the insulation fall off the wires or whatever.
Did you say you got a frame stiffener? Bet half the reason your frame cracked is your hanging a battery on the front of it and flexing it.
I notice that many use the 3.17 mm shaft. Do you know if that shaft dia uses the same pitch gears as out little 2.3 dia shafts? I think they say somewhere that the 3.17 shaft uses a .50 pitch gear.